Art of cracking hydrocarbons



J. W. COAST, Jn.

ART 0F CRACKING lHYDROCARBONS.A

APPLICATION min SEPI. 27, 1917.

' ,349,8 1 6 Pfelltd Allg. 17, 1920.

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UNlTED STATES PATENT OFFRE.

JOHN W. COAST, JR., OF TULSA, OKLAHOMA, ASSIGNOR TO THE PROCESS COMPANY,

. OF TULSA, OKLAHOMA, .A CORPORATION OF MARYLAND.

ART OF CRCKING I-IYDROCARIBONS.

To all whom it may concern:

lle it known that I, JOHN W. CoAs'r, Jr., a citizen ofthe United States of America, a resident of Tulsa, in the county ot Tulsa, State of Oklahoma, have invented certain new and useful Improvements in the .Art ot 'Cracking Hydrocarbons, of which the tollowin is a full, clear, and exact description, reerence being had to the accompanying drawings, :forming a part of this speciiication. v i

This invention relates'to improvements in the art of cracking hydrocarbons, and more particularly to a method involving the use oit a liredieated cracking still wherein a body oit hydrocarbon oil is conlined under pressure.

While the oil is undergoing distillation under high pressure and at a high temperature, a heavy carbonaceoussubstance known as colte and coke-'forming matter drops by gravity and settles on' the bottom of the still. This heavy substance is a heat insulater and it is usually permitted to accumulate on .the hot still bottom, directly above the lire, thus preventing' the tree `transniission of heat trom' the still bottom to the oil. One of the important problems in this art lies in the elimination of the danger andexpense due to the presence of large bodies of' coke-formino matter on the hottest parts of'cracking stills. In tollowing the ordinary practice it is necessary to increase the temperature of the still bottom as the cracking operation progresses, so as to maintain the oilat the necessary high temperature. As a consequence, the still bottom is liable to be overheated and become redhot, and in this event some immediate steps must be taken to avoid a rupture at tbe overheated portion of the still. IThe still may be cooled and the operation discontinued for thepurpos'e of removing the residue, or the cracking operation can be continued at a lower temperaturen Obviously, both oi 'these steps are'very undesirable.

The accumulation of colte-tormiug matter on the hottest part of the cracking still is therefore a source oit danger, and it results in many losses. A waste ot iiel results trom the transmission ot heat through thefthiclr body oit insulating matter, and the lite oit the still is decreased by exposure to high temperatures. .,Howcver, the greatest loss is due to the "fact that the necessary Specication of Letters Patent.

Patented Aug.` 17, 1920.

- Application filed September 27, 1917. Serial No. 193,470.

forming matter, a very large volume of unconverted and partially converted hydron carbone remain in the cracking still as residue, instead of being transformed into the desired low boiling point product.

My objects are to avoid the danger and heat losses which have resulted from the presence oit coke-forming matter in large cracking stills; and to craclr and distill the oil very rapidly, thus increasing the capacity of the still. However, a most important: advantage lies in the greatly increased yield of low` boiling point hydrocarbons, which l obtain by maintaining lthe oil at the necessaryv high pressure and temperature, until it no longer respondsreadily to the cracking ltreatment. The statements con tained herein, as to they greatly increased yield, have been borne out by actual results obtained by the use ot the invention in ordinary cylindrical craclriiig stills.

In the preferred torni oit the invention, all of the foregoing advantages are ob tained by confining a body of hydrocarbon oil in a large horizontal cylindrical tirehea'ted cracking still, the arcuate bottom ol the still being exposed to the lire, maintaining` the contents of the still at a high pres.

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sure and at a high temperature, and at the 'bottom to the oil, and the high temperature can be maintained without overheating. the still. ln addition to greatly increasing the yield of low boiling point l'ractions, and obtaining the other advantages referred to above, l'. have Afound that the cracking oper ation can be carried on continuously :tor considerable period of time, by introducing a 'fresh charge into the still without remote lilo lll)

ing the coke-forming matter from the original charge.

I am aware that scrapers have been used in stills wherein crude petroleum, shale, etc., is treated under atmospheric pressure, but the conditions in such stills are radically different from the conditions existing in a cracking still where a high boiling point product is subjected to high pressure and Vaporized to form a low boiling point product. I believe it is new to crack petroleum hydrocarbons under pressure, as herein disclosed, and at the same time sweep the coke-forming matter from one part of the still to another. Furthermore, this new method has resulted in a yield much greater, I believe, than that obtained by any other known method of cracking hydrocarbons. In other words,` I believe the method is new and that it affords a solution of the greatest problem. in this art.

Figure I isza diagrammatical view of a cracking apparatus adapted for use in following the new method;

Fig. II is an enlarged transverse section of the cracking still.

Fig.. III is an enlarged fragmentary detail View showing a portion. of the still bottom and one of the chains resting thereon.

The apparatus shown to illustrate the invention comprises a large horizontal cylindrical cracking still 1, arranged above a heating chamber 2 and connected, by means of a vapor pipe 3, to an air cooled reflux condenser 4:. 5 designates a vapor pipe lead# ing from the reflux condenser to a water cooled condensing coil 6 from which the low boiling point product is recovered.

The apparatus herein shown is particularly adapted. for use in cracking high boiling point products of distillation, such, -for example, as distillates or residues resulting from the distillation of crude petroleum.

The oil to be treated may be introduced into the still in any suitable manner, and any de'- sired pressure may be obtained by regulating a valve 7, preferably arranged in the vapor pipe 5. The pressure in the still is preferrably greater than three atmospheres, for example, about 80 pounds .per square inch, and the temperature of the contents of the still preferably ranges from about 600 F. to 800 F. The arcuate bottom of the still is exposed directly tc the lire in the heating chamber 2.

While the oil is undergoing distillation under a high pressure and at a high temperature, heavy coke-iorming matter will accumulate in the still and tend to settle on the arcuate bottom, directly above the tire, as previously pointed out. To avoid the danger and expense heretofore incurred by the presence of the coke-forming matter. at the same time very greatly increasing the yield of low boiling point fractions, I continually sweep the coke-formin part of the still to anot ier. The sweeping device herein shown comprises four long chains 8 arranged on the arcuate lower portion of the still and extending approximately from one end of the still to the other. Pairs of diverging arms 9, depending from an oscillatory shaft l0 at the center of the still, are connected at their lower ends to arcuate angle 4bars 1l. The ends of the long chains S are fastened to the angle bars 1l near the ends of the still, and short chain sections l2 may be used to connect the chains to the angle bars 11 near the middle of the still. The shaft 10 extends through a stuffing box 13 at one end of the still, and it may be oscillated by transmitting power through a link ll to a crank or operating arm l5 at the outside of the still. This shaft 10 is oscillated continually so as to' drag the long, heavy chains 8 back and forth across the arcuate still bottom, thus sweeping coke-forming matter from the middle to the sides of the still. The links of the chains 8 are preferabl square in cross section, as shown in Fig. II to provide a number ci' sharp corners which act very eilectively on the coke-forming matter tending to adhere to the arcuate still bottom. Actual experience has shown that large bodies of coke-forming matter will accumulate at opposite sides oi the still instead of collecting on the hottest part oi the arcuate still bottom. This insulating matter is thus swept from the fire heated bottom of the still and permitted to accumulate in the still at relatively high elevations, where it will not materially interfere with the transmission of heat from the lire to the oil. The cracking operation can therefore be continued lon enough to obtain a greatly increased yield from the heavy oil. and since the danger of overheating the still is almost entirely eliminated, the oil can be distilled very rapidly.

l 'have herein disclosed a specific method which I know will obtain the increased yield and many other advantages, and have endeavored to state the reasons for such results. However.` there may be other contributory reasons et which I am notlaware; for the precise actions of the hydrocarbons undergoin c cracking treatment are not undern stoo and it is possible that the highly successful treatment is due, partly, to some other advantageous action resulting from the agitation and sweeping of the coker'orming matter while the body of oil is subjected to the cracking treatment.

l claim:

ln the artA of cracking petroleum hydrocarbons, the method which comprises conining a body of hydrocarbon oil in a large horizontal cylindrical fire-heated cracking still. the arcuate bottom of the still being exposed tcthe re, maintaining the contents matter from, one y of said still under a pressure greater than three atmospheres, condensing the vapor passing from the still, at the same time continually scraping coke-forming matter across the fire-heated arcuate bottom, from the middle to opposite sides of the still, and per'- mitting such coke-forming matter to accumulate in the still at relatively high elevations beyond the hottest portion of said arcuate bottom. 10

In testimony that I claim the foregoing I hereunto affix my signature.

JOHN W. COAST, JR. 

